The major emphasis of this research involves an analysis of type C RNA virus expression in different mammalian species, investigation of cellular regulatory controls influencing expression of endogenous type C RNA viruses, and determination of the possible etiologic role of RNA type C viruses in natural tumors of their hosts. The eventual goals of these studies will be aimed towards the development of rational approaches to prevention of human cancer. BIBLIOGRAPHIC REFERENCES: Stephenson, J.R. and Aaronson, S.A.: Induction of an endogenous B-tropic type C RNA virus from SWR/J mouse embryo cells in tissue culture. Virology 70: 352-359, 1976. Phillips, S.M., Stephenson, J.R. and Aaronson, S.A.: Genetic factors influencing mouse type C RNA virus induction by naturally occurring B-cell mitogens. J. Immunol. 118:662-666, 1977.